This invention relates to an improved process for manufacturing bent knives for certain wood cutting machines such as long slabbing chippers and lumber edging chippers.
For example, a log slabbing chipper having a plurality of bent knives is illustrated in my U.S. Pat. No. 4,082,127. The knives in such machines must be removed for sharpening and when they cannot be sharpened further they must be replaced with new knives. Thus the cost of knives is a substantial factor in the cost of operating the machine. This cost is often increased by breakage of the knives, such breakage frequently occurring in the bend in the knife.
The conventional sequence of steps of manufacturing such knives is to cut the steel to size, semi-finish, heat and form to a specified angle of bend wherein the bend line is transverse to the cutting edge, heat treat as necessary and, finally, finish grind the flat faces. The operation of finish grinding the flat surfaces is difficult because according to conventional practice it must be done after forming to the bent shape in order to correct any error in the formed angle of the knife and correct distortions in the bend. Any such angular error and distortion in the forming step must be corrected in the finish grind step.
Because of the thickness of conventional knives they are too stiff to conform to the angle of the holder when clamped in position in a machine if there is any error in the angle of the bend in the knife. Accurate positioning of the knives is essential to the proper operation of the machine.
Objects of the present invention are, therefore, to provide an improved process for manufacturing bent knives in wood cutting machines, to provide a process which is less difficult and expensive than the conventional process, to provide a process which produces knives that are less subject to breakage, and to provide a process in which the operation of finish grinding the flat surfaces may be performed before the bending operation.